Former Chelsea winger Shaun Wright-Phillips scored the winner for the West London side with only 12 minutes remaining which put Chelsea 14 points below League leaders Manchester United.
Rangers won only their second game this season and also their second win under Harry Redknapp as Chelsea ended their four-match winning run. QPR came back from a 3-0 loss to Liverpool at home last time out and registered their first win at Stamford Bridge for two decades.
Chelsea dominated throughout the game while QPR defended and created chances on the break. Adel Taarabt laid the ball prefectly for Wright-Phillips who slammed home in the 78th minute.
This result took Chelsea down to fourth place below London rivals Tottenham while QPR remain bottom of the table on goal difference.
Chelsea suffered their second home defeat this season after the controversial 2-3 loss to Manchester United.